this seems to be a nightmare. Anyone got any pointers tips for getting the contextual menu to pop up once you have selected multiple messages using the touch screen so that you can mark them all as read without having to use the keypad?

I'm not sure why you're so against the keyboard, but you can mark prior messages read by selecting the newest message, pressing the full menu button in the bottom right, and selecting "mark prior read".

Sorry I can't find this full menu button in bottom right

Here:

ok. What I am asking is how do you get that menu to come up when you have more than one message highlighted. I don't need that full menu I just need the mark unread thats in the top right

I misunderstood. You cannot open the menu via the touchscreen when more than one message is selected.

I just select or multi select, then tap/hold and it will show up.

For all messages, I tap and hold the date bar and the menu will pop up.